It is known to warp-knit support tapes for a slide-fastener stringer. A coupling element is then stitched to an edge of each of the tapes. Two such tapes along with their stitched-on coupling elements constitute a slide-fastener stringer that can later be equipped with a slider and end stop members so as to form a complete slide fastener.
Normally each of the tapes is knitted as a so-called stabilized fabric (see U.S. Pat. No. 3,708,836 corresponding to German Published application DT-OS 2,016,141). This knit is normally made of a plurality of chains or pillars formed by so-called warp yarns into which is laid a plurality of weft yarns. A warp yarn here is meant to refer to any filament running mainly in the warp direction and a weft yarn similarly refers to any filament running transverse thereto. Such a fabric offers relatively good dimensional stability, and the valley between the edgemost wale and the adjoining wale has proven convenient for stitching-on of the coupling element.
More particularly, in this arrangement the wales are of the single-bar type formed as warp chains which are bridged only by the filler or weft. As indicated the sole connecting threads or yarns between the warp chains are the laid-in weft filaments or yarns which extend over four warp chains each so that four such weft inlays fill each warp loop to provide the transverse stability of the tape (stability in the plane of the tape perpendicular to the warp chains) and, in addition, prevent longitudinal extension and contraction (change of dimension in the plane of the tape parallel to the warp chains). The dimensional stability is most pronounced if the tapes are composed of synthetic-resin yarn which has been thermofixed, i.e. subjected to a heating or ultrasonic treatment which relaxes internal stress within the yarn.
The advantage of single-bar warp chains, i.e. individual spaced apart wales of loops interconnected only by the weft, is that channels are formed between wales so that the row of stitching for attaching the coupling element can lay along one of these channels or valleys.
The relatively simple knit of the prior art does not make use of the considerable capacity of a modern knitting machine.
Furthermore, such a stabilized fabric is also very likely to ravel, since whenever one of the pillars of the warp yarns is broken ravelling will occur, and any breaking of any of the weft yarns will similarly cause ravelling. Even the slightest amount of damage to a slide-fastener stringer tape using a helicoidal monofilamentary coupling element can result in deformation, that is stretching or squeezing-together, of the turns of the coupling element so as to make the slide fastener produced thereby useless. Finally, the speed with which the coupling element can be stitched to the support tape is limited.